Optical properties of planar metallic photonic crystal structures: Experiment and theory

We report on results of transmission measurements of metallic nanowire arrays deposited on top of different dielectric substrates. The appearance of grating anomalies, which critically depend on the substrate thickness, provides evidence that the optical response of these planar metallic photonic crystal structures can be strongly modified. While only Rayleigh-type anomalies are observed for thin dielectric substrates, thicker waveguiding substrates can induce strong coupling phenomena. This strong coupling results in the formation of waveguide-plasmon polaritons with a large Rabi splitting up to 250 meV. We show that the coupling phenomena vary with the nanowire grating period, the angle of incidence, and also the waveguide layer thickness. A scattering-matrix-based numerical method is used to calculate the transmission properties and the near-field spatial distributions of such metallic photonic crystal structures. All experimental results are well confirmed by our theoretical calculations.